Grain and other relatively free flowing materials are frequently stored in air tight silos or storage structures and are unloaded from the bottom of the silo through use of a bottom unloader. Typically bottom unloaders, as shown in U.S. Pat. Nos. 3,250,407, 3,084,818 and 3,851,774, include a sweep auger which is mounted for rotation about the center of the silo and acts to dislodge the stored material and convey it toward the center of the silo where it is delivered into the inner end of a radially extending trough formed in the silo foundation. A discharge auger or conveyor operates in the trough to convey the stored material to the exterior of the silo.
In the past, the sweep auger has been rotated about the center of the silo in an incremental or stepped manner. To provide this type of incremental movement, a drive unit, located on the exterior of the silo, is connected to a horizontal drive shaft through a ratchet and pawl connection which provides intermittent rotation for the drive shaft. As disclosed in U.S Pat. No. 3,851,774, the drive shaft carries a worm which engages gear teeth formed on a turntable that carries the sweep auger. In this manner, rotation of the drive shaft will rotate the turntable and thereby rotate the sweep auger about the center of the silo.
In the bottom unloaders as used in the past, the sweep auger, in addition to being rotated about the center of the silo, has also been rotated about its axis through a drive mechanism which is taken off of the discharge conveyor. With this type of drive system, rotation of the discharge auger is transmitted to a vertical drive shaft, located at the inner end of the trough, and the upper end of the vertical shaft is connected to the sweep auger shaft to thereby rotate the sweep auger about its axis as it is rotated within the silo.
To aid in delivering the stored material to the discharge auger, the prior bottom unloaders have also incorporated a slinger which has been mounted on the vertical drive shaft at the inner end of the trough. Rotation of the slinger serves to deliver the stored material to the discharge auger where it can be conveyed to the exterior of the silo.